COS-WEB: SUSPICION-DRIVEN MULTI-AGENT REASONING WITH STRUCTURED COMMUNICATION

Large language models (LLMs) are increasingly used for complex reasoning, but a single reasoning path can remain vulnerable to missing knowledge and internally consistent errors. LLM-based multi-agent systems (LLM-MAS) address this limitation through information exchange and collaborative decision-making. MultiAgent Debate (MAD) lets agents critique reasoning paths and revise judgments over multiple rounds. However, agreement on an answer does not guarantee that its supporting rationale is reliable: when multiple agents share an unverified assumption, their interaction may further reinforce a false consensus. Meanwhile, existing communication optimization methods focus mainly on interaction structures, messages, or participant selection. They rarely represent unresolved issues explicitly to guide local communication and subsequent re-examination. To address this, we propose CoS-Web (Chain-of-Suspicion with Spider-Web Communication), a multi-agent reasoning framework that connects suspicion-driven interaction with subsequent communication through structured unresolved issues. Chain-of-Suspicion (CoS) is a suspicion-driven interaction protocol that progressively examines agent judgments, their anticipated defenses, and collective reasoning risks to formulate structured unresolved issues. Spider-Web Communication uses these issues to organize local Ring Communication among relevant agents on top of Radial global-state sharing, and re-examines whether the issues remain unresolved after communication. Experiments and analyses across multiple reasoning benchmarks show that CoS-Web improves overall reasoning accuracy while balancing communication costs, and handles cases in which multiple agents share erroneous assumptions more robustly